Portable electronic instruments used for radiation detection have calibrating adjustments to align electronic components and meter readings, which should be calibrated frequently in view of potential changes of battery and electrical component tolerances. However under usual conditons encountered in the field, convenient portable calibration apparatus is not available, primarily because of the possible exposure of unskilled operators to radiation damage. However, if an instrument is not in calibration, erroneous readings could impose significant damage. Thus, it is an objective of this invention to provide an improved, convenient to use, calibrating apparatus that can be used safely in the field without skilled operators, and which is small and portable.
Calibrating apparatus for radiation sensing instruments is known in the prior art, as exemplified by British Specification 37758/62 published Mar. 3, 1965 by K. E. G. Perry for Improvements in or relating to Calibration Device for Calibrating Radiation Sensitive Instruments. A portable or wall mounted instrument is provided using a beta radiation source with an adjustable calibrated shutter detented at several positions for exposing the radiation source at different radiation intensities for calibrating different instrument detection ranges, by means of holes of different sizes. A beta source is used to reduce the amount of shielding required for a gamma radiation source. This instrument however cannot safely be used in the field with untrained personnel because fo the direct exposure of personnel using the device to the radiation from the source which is directed outwardly into the environment and toward persons using the device for calibration through the calibration holes. Also there is no provision in the apparatus for preventing the beta source from converting the beta radiation to harder X-Ray or gamma radiation, as will be explained in more detail hereinafter.
U.S. Pat. No. 2,820,905, Jan. 21, 1958 to B. Schloss for Radiation Detector Calibration is also deficient in safety measures in that a radium bromide radiation source is contained within the instrument for manual transfer to the carrying handle for calibration and therefore must be handled during calibration without protection of the calibrating personnel or the surrounding environment from radiation.
French publication 2,360,869, Mar. 3, 1978 provides wall mounted calibration apparatus with a gamma source in a thick walled lead housing which however radiates into the environment towards a person calibrating an instrument through calibrated windows in doors, which are manually opened.
This invention is directed toward the provision of safe and secure calibration apparatus that does not expose personnel or the environment to the dangers of radiation.